Immunotherapy, better known as allergy shots, has long been a treatment option for certain allergies.

Allergies arise from an immune system reaction against a normally benign substance, such as plant pollen.

And immunotherapy is designed to help the immune system develop a tolerance for the culprit substance, by exposing the body to tiny amounts of it over time.

An edible, plant-based vaccine would have a number of advantages over allergy shots, the most obvious being the lack of pain, says Dr Fumio Takaiwa, the senior author on the new study.

First, make your vaccine

He and his colleagues created their vaccine using small pieces of certain allergy-related proteins found in Japanese cedar pollen, a common trigger of hay fever in Japan.

By inserting genetic material from these proteins into the rice genome, the scientists cultivated rice that contained the pollen proteins.

They then fed a group of mice the rice-based vaccine every day for several weeks before exposing the animals to Japanese cedar pollen.

The researchers found that compared with mice that did not eat the rice, those that did showed far less of an immune reaction against the pollen. They produced less histamine, the chemical that triggers hay fever symptoms, and sneezed less often.

Much research is now going toward so-called biopharmaceuticals, medicines and vaccines that are mass-produced using genetically modified plants.

Earlier this year, scientists reported that a potato engineered to carry a hepatitis B vaccine seemed to work in the first group of human volunteers to dine on the spud.

Many scientists believe that engineering plants to produce therapeutic proteins will allow for a simpler, cheaper way to mass-produce and administer drugs and vaccines.

Traditional vaccines are created using cells as incubators; these cells may come from animals or bacteria, for instance, and the vaccine substances must be extracted and purified.

With plant-based vaccines, Takaiwa notes, there is no need for the complex purification process.

In addition, he says, the rice-based pollen vaccine could be safer than traditional allergy shots because it is more finely tuned; it uses only small bits of the pollen protein that do not attach to the antibodies a hay fever sufferer's body produces.

This means it would be less likely to produce a potentially life-threatening reaction called anaphylaxis, a risk with allergy shots.

Still, Takaiwa acknowledges the widespread public concern over genetically modified crops, and says that it will be "very important" to create systems that prevent pharmaceutical crops from accidentally contaminating those heading for the supermarket.